Speaker
Description
Inelastic dark matter (iDM) consists of two almost mass-degenerate states with a small mass splitting and has been widely studied for its unique phenomenology. We consider iDM with a light dark photon/lepton-specific scalar mediator which feebly couples to the Standard Model particles. iDM is produced by freeze-in: the couplings are too small to put iDM in chemical equilibrium but can still gradually generate it to the observed abundance. Since the mediator is lighter than iDM, the coupling for DM abundance directly relates to the decay rate of the heavier state. The mass-splitting smaller than two electron masses and feeble couplings make the heavier state cosmologically long-lived. The suppressed decay of the heavier state emits three/two photons, which can be detected by an X-ray telescope. We conduct the Bayesian analysis of the 16-year data from the spectrometer onboard the INTEGRAL telescope using python-based platform 3ML; we then set the limits for the coupling of 100-MeV scale dark photon/lepton-specific scalar mediator and GeV-scale iDM. The resulting constraints are complementary to those from the existing collider and beam dump experiments.